Dr. William Bayer, MD

Dr. William Bayer, MD

Endocrinology, Diabetes & Metabolism  |  
Male  |  
56 y/o

Accepting new patients

Dr. William Bayer, MD is an endocrinology, diabetes & metabolism doctor who practices in Carol Stream, IL. He is 56 years old and has been practicing for 31 years. Dr. Bayer is affiliated with Northwestern Medicine Central DuPage Hospital.

Northwestern Medicine Regional Medical Group

501 Thornhill Dr

Carol Stream, IL 60188
Get Directions

Accepted insurance

  • Aetna
  • Blue Cross Blue Shield of Illinois
  • Cigna
  • Cigna-HealthSpring
  • CorVel
  • Coventry Health Care
  • First Health (Coventry Health Care)
  • HealthLink
  • HFN
  • Humana
  • LifeSynch
  • Medicaid
  • MultiPlan
  • UniCare

Learn about Dr. Bayer

Care Philosophy

"Better people means better experiences. Our care team is committed to delivering results that change lives." 
...Read More

Dr. Bayer's Experience

Dr. Bayer's experience matches your search based on the following criteria:
  • Based on total number of patients treated over the last 12 months
  • Specializes in Endocrinology, Diabetes & Metabolism
  • Board certified in Diabetes, Metabolism & Endocrinology and Internal Medicine
  • No malpractice claims found
  • No sanctions found
  • No board actions found


  • Endocrinology, Diabetes & Metabolism

Board Certifications

  • Diabetes, Metabolism & Endocrinology
    Accredited by: American Board of Internal Medicine*
  • Internal Medicine
    Accredited by: American Board of Internal Medicine*

Conditions Treated

  • Abnormal Thyroid
  • Acromegaly and Gigantism
  • Adrenal Gland Diseases
  • Adrenal Incidentaloma
  • Adrenal Insufficiency
  • Autoimmune Diseases
  • Autoimmune Thyroid Diseases
  • Benign Tumor
  • Bone Disorders
  • Breast Diseases
  • Calcium Metabolism Disorders
  • Cancer
  • Congenital Adrenal Hyperplasia (CAH)
  • Cushing's Syndrome
  • Diabetes Insipidus
  • Diabetes Type 1
  • Diabetes Type 2
  • Diabetes With Renal Manifestations
  • Goiter
  • Gynecomastia
  • Hashimoto's Disease
  • Hypercalcemia
  • Hyperlipidemia
  • Hyperparathyroidism
  • Hyperthyroidism
  • Hypokalemia
  • Hypoparathyroidism
  • Hypopituitarism
  • Hypothyroidism
  • Kidney Disease
  • Lipid Disorders
  • Malaise and Fatigue
  • Menstrual Disorders (incl. Dysmenorrhea)
  • Multiple Endocrine Neoplasia
  • Obesity
  • Osteopenia
  • Osteoporosis
  • Parathyroid (Gland) Disease
  • Phosphorus Metabolism Disorders
  • Polycystic Ovarian Syndrome
  • Symptomatic Menopause
  • Testicular Dysfunction
  • Thyroid Cancer
  • Thyroid Cyst
  • Thyroid Disease
  • Thyroiditis
  • Vitamin D Deficiency


Read More


  • Continuous Glucose Monitoring
  • Diabetes Counseling

Background Check

0 Malpractice Claims

No malpractice history found for Illinois.

0 Sanctions

No sanctions history found for the years that Healthgrades collects data.

0 Board Actions

No board actions found for the years that Healthgrades collects data.


  • Loyola University Of Chicago / Stritch School Of Medicine
    Medical School | Graduated 1986
  • Loyola University Medical Center
    Internship Hospital | Completed
  • Loyola University Medical Center
    Residency Hospital | Completed
  • Loyola University Medical Center
    Fellowship Hospital | Completed

Awards & Recognition

Awards & Honors
  • Healthgrades Honor Roll
Media & Publications

Dr. Bayer has no media or publications listed.

Languages Spoken

  • English

Memberships & Professional Affiliations

Dr. Bayer does not have any memberships or affiliations listed. If you are Dr. Bayer and would like to add memberships or affiliations, please update your profile.

Dr. Bayer's Reviews

Likelihood of recommending Dr. Bayer to family and friends
based on 24 total reviews (10 with comments)
Dr. Bayer's Performance
  • Trustworthiness
  • Explains condition(s) well
  • Answers Questions
  • Time well spent
Office & Staff Performance
  • Scheduling
  • Office environment
  • Staff friendliness
  • Average wait time
    16 to 30 minutes
Patient Comments (10)
in St. Charles IL. |
Dr. Bayer is a Diabetic Endocrinologist that I have complete trust in has really turned my A1C Goal/Goals to the Positive. He is very knowledgeable in his field and he always spends appropriate time w/patient/patients. I will be 62 in December and have been battling Diabetes since 1999/2000. He has also been a big influence on how I feel about my condition-always Positive. He has my Thanks! Bryan Compton
Do not take the bad reviews seriously! Dr. Bayeris amazing & caring! So, if you need a really good doctor that cares about your health & does not set a timer when you walk in, he is your answer to getting your health back on track! I came to him when there was no one else. He cared & I am now on my way to not only answers but resolutions. He has a good heart & is a briliant doctor! If you are serious about working on your health & learning how to be healthier but need a coach; he is for you!
Hoffman Estates, IL |
Dr Bayer is a no-nonsense doctor that is very knowledgable and thoruough. I have gone to him for many years before a car accident and am now able to see him again. I could not find his phone number so I looked it up. As I read the reveiws that were positive, I could relate. As I read the negative reviews I wondered what could have gone wrong. I made my appointment a little concerned. Well, I can only say that Dr. Bayer is still the caring wonderful doctor that I remember.
in Aurora, IL |
He needs to retire. He's clearly mad at everything, he was 30 minutes late to an 8:00 am meeting and told me out of the gate he already didn't know what to do. He took no time to listen and understand. he's terrible, go somewhere else
Wheaton, IL |
One of the worst doctors I have ever seen. Rude, disrespectful, and just plain mean. He doesn't care about patients and this was shown by his horrible bedside manner. He needs training on how to be nice to people.
Chicago, IL |
Dr. Bayer is so nice. He listens and is excited when he sees me progressing in my health. Worked consistently to get my thyroid medication to the appropriate level.
IL |
Rude bedside manner, rushes through, and was annoyed when I had to mention multiple health issues. He really seems to hate his job. Probably competent with thyroid issues but just too rude and unhappy!
Aurora, IL |
Dr Bayer acted like a robot. Dr Bayer made eye contact 5 seconds during the entire appointment. He spent all his time filling out forms on his computer instead of listening to any concerns I had. His bedside manner is horrible, he is extremely unwilling to entertain other professional opinions. He was very concerned about if insurance will cover instead of the care of the patient, save yourself the frustration find a different doctor who cares about your health & issues.
in Aurora, IL |
Everything I heard about Dr. Bayer from other Doctors and the general public is true. He will take the extra mile on getting to the root of your issues. I felt comfortable with his personality and concern for my health and well being.
Wouldn't recommend.
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Now Accepting New Patients
Dr. Bayer accepts 16 insurance carriers
  • Aetna
    Aetna EPO
    Aetna POS
    Aetna PPO
    Managed Choice POS
    Open Choice PPO
  • Blue Cross Blue Shield of Illinois
    Blue Advantage
    Blue Cross Blue Shield of Illinois HMO
    Blue Cross Blue Shield of Illinois PPO
    Blue Precision HMO
  • Cigna
    Great West Healthcare-Cigna HMO
    Great West Healthcare-Cigna POS
    Great West Healthcare-Cigna PPO
  • Cigna-HealthSpring
  • CorVel
    Worker's Compensation WC
  • Coventry Health Care
    Coventry Health Care HMO
    Coventry Health Care POS
    Coventry Health Care PPO
  • First Health (Coventry Health Care)
  • HealthLink
    HealthLink HMO
    HealthLink POS
    HealthLink PPO
  • HFN
    Worker's Compensation WC
  • Humana
    Choice Care
    Choice PPO
    Humana HMO
    Humana POS
    Humana PPO
  • LifeSynch
    Behavioral Health
  • Medicaid
  • MultiPlan
    MultiPlan PPO
    PHCS Network PPO
  • UniCare
    UniCare HMO
    UniCare POS
    UniCare PPO
  • UnitedHealthCare
    Choice Plus
    United Behavioral Health
    United Healthcare EPO
    United Healthcare HMO
    United Healthcare POS
    United Healthcare PPO
  • Viant

*Please verify this information when scheduling an appointment.

Hospitals where Dr. Bayer has admitting privileges

Northwestern Medicine Central DuPage Hospital
25 N Winfield Rd
Winfield, IL 60190
View Hospital Profile

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